1. Field of the Invention
The present invention relates to a film or sheet forming apparatus, and particularly, to a film or sheet forming apparatus for film or sheets relatively thin and needing a high degree of precision in thickness, such as for an optical use.
2. Relevant Art
The film or sheet forming apparatus for films or sheets relatively thin and needing a high degree of precision in thickness, such as for an optical use, is typically installed in a clean room, and configured such that a resin delivered from a die which holds molten resin is received simply with an outer peripheral surface of a resin receiving roll, and the roll is driven to rotate about its central axis, so that the resin is fed to be guided by the outer peripheral surface of the roll, while being cooled to an adequate state of solid phase, whereby a film or sheet is formed.
In other words, this type of film or sheet forming apparatus has a roll which is driven for rotation about its own central axis, and an outer peripheral surface of the roll is given a resin from a die, which resin is cooled with the outer peripheral surface of roll to form a film or sheet.
In order to provide the film or sheet with a maintained thickness precision, various measures have been devised.
For instance, a formation starting point (as an angular position) where the resin from the die is brought into contact on the roll outer peripheral surface is stabilized in its transverse direction by appropriate techniques (e.g. air knife method, width pinning method, edge pinning method, edge blasting method) to prevent the cooling by roll from varying.
Further, a compartment is provided to accommodate the forming apparatus with a die inclusive, and a door or curtain is furnished for entry or exit of worker thereto, so that the formation of film or sheet is free from influences of air conditioning in the clean room.